The background description provided here is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Substrate processing systems may be used to deposit and etch film on a substrate such as a semiconductor wafer. The substrate processing systems typically include a processing chamber, a gas distribution device and a substrate support. During processing, the substrate is arranged on the substrate support. Different gas mixtures may be introduced into the processing chamber and radio frequency (RF) plasma may be used to activate chemical reactions.
Double patterning approaches may be used for pitch splitting. A core layer is deposited and patterned to define a plurality of spaced cores. A conformal layer is deposited on the cores. Then, the conformal layer is etched using an anisotropic etch process to etch most of the conformal layer while leaving behind spacers on sidewalls of the cores. The cores are selectively etched. Then, a critical dimension (CD) of the spacers is transferred to a lower layer.
After etching, the shape of upper portions of the spacers is asymmetric primarily due to ion sputtering during the anisotropic etching. As a result of the asymmetric shape, there is increased variability in the critical dimension (CD) when transferring to the lower layer. If additional pitch splitting is performed, the mask is usually transferred to the lower layer to create a squared shape.